Let’s talk about talc!
Talc is a naturally occurring mineral that is accused of being a carcinogen. Like with many accused compounds, talc has been at the forefront of some major news articles and even a few lawsuits! You might have heard about the famous lawsuits against the Johnson & Johnson’s baby powder, however, while I don’t have access to the actual court case papers and I’m going by what the media reported, the cases were not as simple as they sound. The reason for the lawsuits was not always due to talc. There were also some allegations that talc was contaminated with asbestos, which we now know that is harmful. What makes the lawsuits worse is that there are also some allegations that employees at Johnson & Johnson’s knew about the contamination and did nothing. Nevertheless, some of the cases are still on going and the company is still appealing. There is even a case that was dismissed as a mistrial because the jurors could not reach a decision.
Contamination is a separate issue that can happen to any compound or product (even food), healthy or not, and it comes down to how good the quality control of a company or procedure is. This is a separate issue that will be discussed in another post. Talc used in cosmetics is and should be, highly purified. 
For now, let’s have a look at the scientific evidence on talc. Is it actually harmful?
Talc has been used in cosmetics for years and many, scientists and others, use this argument to state that it has a long proven history of use and therefore, is safe. 
The quantity of a compound that we are exposed at is also very important in determining whether it is harmful or not. As I explained in previous posts, even water can kill you if you drink between 6-10 liters within a couple of hours. A research paper published in the Regulatory Toxicology and Pharmacology journal states that the amount of talc we are exposed to in cosmetics is at least 350 times lower when compared to industrial exposure. 
Like a lot of cosmetic compounds, talc is also used for pharmaceutical and food applications. [1, 3] However, talc has been utilised in a lot in cosmetics due to its soft nature, its actual structure (a sheet-like structure of layers that are held together by weak forces and give a moisturising or slip-like feeling when rubbed against each other) and its ability to cover blemishes while being translucent.  Like many materials, talc can be found in different particle sizes, depending on the type of product and manufacturer. However, particle size, in this case, does not make a difference in human exposure risks as they are often encapsulated by other ingredients and therefore, cannot be breathed in as a powder. Breathing in any powder, especially talc and silica is indeed harmful and can cause irreversible lung damage. As a result, if you are really concerned about talc and silica, my advice to you as a chemist would be to avoid loose powders (like setting powder products) that contain them.
Talc is classified as “Not a hazardous substance or mixture according to Regulation (EC) No. 1272/2008.” in its Material Safety Data Sheet (MSDS – these sheets are what chemists use to identify the risks of compounds) but good laboratory practise consults to “Avoid dust formation. Avoid breathing vapours, mist or gas.”.  This is not because talc is actively doing something harmful but rather due to the fact that many powders that enter the lungs will stay there for ever, clogging your lungs over time. Studies following exposure of talc in miners have shown that talc dust may cause gastrointestinal irritation. [3, 4, 5] However, note that the amount of talc that miners are exposed to is nowhere near the one found in cosmetics and the exposure method is by inhalation.
The US Food and Drug Administration, FDA, states that talc in cosmetics is safe and any harmfulness would come if talc was contaminated with asbestos.  They also released a list of some cosmetics that they have analysed, including the Johnson & Johnson’s baby powder, but didn’t find asbestos in them.  Similarly, the Cosmetic Ingredient Review Panel, CIR, also looked at the available scientific data on talc and concluded that it is safe to use in cosmetics in concentrations up to 100%.  However, they stated that talc should not be used when the epidermal skin layer is missing or damaged,  and therefore should be avoided by sensitive skin suffers. The International Agency for Research on Cancer, IARC, stated that “There is inadequate evidence in humans for the carcinogenicity of inhaled talc not containing asbestos or asbestiform fibres.”.  However, they also stated that “There is limited evidence in humans for the carcinogenicity of perineal use of talc based body powder.”. 
The latter, usage of talc around the genial areas has been one of the biggest concerns about talc. A large part of the lawsuits against Johnson & Johnson’s, has been claims that talc, found in their baby powder, can cause ovarian cancer when used at the genital areas. However, while IARC stated that there is limited evidence, a study carried out in 2000, following (since 1976) amongst others, 121 700 female nurses concluded that there was no association between ever using talc powder and a risk for ovarian cancer.  There was also no increasing trend of ovarian cancer with talc usage. I could list a lot of studies here but I think you get the overall picture. While talc in cosmetics is safe, there is still an ongoing scientific debate and contradicting evidence around the use of talc in genital products.
Another company that made headlines, at least in the beauty community, around the use of talc is bareMinerals. One of the biggest “controversies”, as considered by some, bareMinerals, a brand committed to “clean beauty” but includes talc in some of their products. However, if you ask me, I think that is fair enough because (a) there is no evidence to convict talc in cosmetics and (b) talc is a mineral and therefore, matches the bareMinerals branding. The only question mark would be if bareMinerals ever stated to be talc-free but from what I can see the only statement on their website is the “clean beauty” one, which is a term that is not strictly defined and could be interpreted in many ways.
Overall, talc, that is not contaminated with asbestos, found in cosmetics is safe to use, especially considering the small amounts we are exposed to. However, if you want to be extra safe, you can avoid talc in loose powders. The association of talc and ovarian cancer, when it is used in products around the genital areas, is still debatable and there are studies on both sides, meaning that it is up to you whether you’d prefer to avoid talc in the genital areas.